1. Field of the Invention
The present invention relates to a uniform aerosol deposit sampling device. In which, the flow guiding portion makes the entire air flow smooth and evenly distributed. The aerosols will be evenly distributed and uniformly deposited on the filter surface. And, it is easy to evaluate the amount and composition of the aerosols.
2. Description of the Prior Art
Referring to FIGS. 7 and 8, a typical conventional atmospheric aerosol sampling device comprising:
a first body 81 including a first connecting portion 811 and a fist through-hole 812;
a second body 82 including:                a second connecting portion 821 for allowing the second body 82 and the first connecting portion 811 be connected together;        a first-staged flow guiding portion 822 disposed in the second body 82, the first-staged flow guiding portion 822 having an air-penetratable supporting pad 91 and a filtering media 92;        a second-staged flow guiding portion 823 disposed in the second body 82, the second-staged flow guiding portion 823 being lower than the first-staged flow guiding portion 822, and the first-staged and second staged flow guiding portions 822, 823 being shaped as a step-like structure in the second body 82;        a second through-hole 824 being connected with the first through-hole 812, the first-staged flow guiding portion 822 and the second-staged flow guiding portion 823.        
An aerosol size-selective sampler 93 is mounted on the first body 81. This aerosol size-selective sampler 93 communicates with the first through-hole 812. There is an air pump 94 disposed on the second body 82. Once the user turns on the air pump 94, this pump will draw the air in (it also sucks in many aerosols 95, as illustrated in FIG. 9). After which, the air continues to pass through the filtering media 92 and then to pass through the first-staged and second staged flow guiding portions 822, 823. Finally, it will be sucked out by the air pump 94 through the second through-hole 824. Therefore, these aerosols 95 will deposit and stay on the filter media 92. After certain time, the filter media 92 can be taken out. By counting or calculating the total number of the aerosols 95 stayed on the filter media 92, it can predict the exact concentration of the aerosols 95 in this working environment. Of course, it also can be measured by a conventional X-ray detecting method or any other available existing method to calculate the concentration or amount of the aerosols 95.
However, about the above-mentioned conventional device, it has many disadvantages or problems as listed below.
[1] the flowing air is not evenly distributed. The step-like structure is constituted by the first-staged and the second staged flow guiding portions. So, when the air flows through them and through the filter media, they will cause some pressure differences in the air stream. Thus, it will influence its flowing direction, and flowing pattern. Therefore, the flowing air is not evenly distributed and always lead the air streamlines to become turbulent or to have vortices.
[2] These aerosols cannot be evenly distributed on the filter media. It is primarily caused by its non-uniform air flowing through the filter media. The air passes through the first-staged and second-staged flow guiding portions 822, 823. However, the flow rate of the air will not be evenly distributed due to the step-like structure. For example, the aerosol distribution in the third position P3 and aerosol distribution in the fourth position P4 are not evenly distributed (referring to FIG. 9 and to the enlarged illustration in FIG. 10). Consequently, aerosols could exhibit non-uniform deposition on the filter, and this occurrence also tends to influence even more the overall precision and accuracy of the analytical process.
[3] It is hard to count or calculate the aerosol amount. As show in FIG. 10, the amount of the aerosols 95 in a specific zone (or region) on the filter media 92 can be counted and evaluated by a microscope 96 and statistical methods, respectively. However, the aerosol concentrations in different zones of the filter media 92 are quite different, so it is very hard to evaluate the aerosol amount precisely. If someone selects one smaller zone to count the aerosol mount and then statistically predict the aerosol amount on the entire filter media 92. The result will be inaccurate. If someone randomly selects several smaller zones at different locations on the filter media 92, this person needs to multiply certain number to calculate the total aerosol amount on this filter media 92. It is troublesome to count or evaluate the aerosol amount.